The present invention relates to a data base system including a plurality of information processing apparatuses connected to a network.
Data base systems have been broadly used, for example, in information systems of a firm, between firms, and of self-governing bodies or local governments to mange personal information and information of personnel affairs such as names and phone numbers as well as to manage parts in factories. One of the database systems employed to manage personal information and information of personnel affairs is a directory system to provide a directory service.
To achieve smooth communication in a firm and between firms, there has been recently adopted an electronic mail (e-mail) system in various fields to communicate via a network such as a local area network (LAN) documents produced by an information processing apparatus, for example, a personal computer (PC). In the e-mail system, the directory service representatively stipulated by X.500 (ISO9594) of the CCITT recommendations has been put to use as an electronic phone book to search a mail address of a receiver.
The directory service conforming to X.500 includes a data model hierarchically controlled in a directory tree. The model includes branches and leaves to which directory entry is allocated as a data unit corresponding to a record in a database. Each entry is specifically identified by a name including hierarchy information, i.e., a distinguished name (dn). The entry may contain a mail address of the user and various information items as attributes of the user such as a name, a phone number, a facsimile number, and a photo.
X.500 adopts a distributed system architecture of client-server type and stipulates a directory access protocol (DAP) in a seven-layer configuration of open systems interconnection (OSI) as a communication protocol between information processing apparatuses functioning as a client or a server. The Internet Engineering Task Force as an organization for standardization of the internet standardized a protocol between a directory client and a server on TCP/IP, i.e., Lightweight Directory Access Protocol (LDAP; RFC2251). From an application program on a client, the user accesses the directory server such as X.500 according to DAP or LDAP to search necessary information such as a mail address of a partner user. The DAP or LDAP further stipulates directory update requests including addition and deletion of an entry, change of an entry name, and update of an attribute value.
As described in page 258 of xe2x80x9cUnderstanding X.500 The Directoryxe2x80x9d published from CHAPMANandHALL, X.521 of the X.500 series recommendation stipulates object class groupOfNames and groupOfSpecificNames to classify entries into groups each including one or more entries. The disclosure of which is hereby incorporated by reference.
For each class, a member attribute is defined to hold an identifier name (dn) of another entry. The member attribute serves as a so-called pointer to indicate another entry. The group entry function makes it possible to classify users and other items registered to the directory server into groups according to various points of view. In the directory service, the group entry is used, for example, to set a directory access right to a plurality of users at a time.
In the information processing system of today, the information to specifically identify another object is called xe2x80x9clinkxe2x80x9d. In the directory service field, an identifier name indicating the object is used as information to specifically identify another object, i.e., as a link not only in the group entry but also, for example, in a meta-directory system. In a relational database (RDB), a name and/or a number which are/is as a primary key correspond/corresponds to the link.
A meta-directory system is a technique to integrally and centrally control, by the directory service, user information of various applications such as the e-mail in a firm. xe2x80x9cDATAMATIONxe2x80x9d published on May 1, 1996 from DATAMATION describes specific products of the meta-directory system in pages 48 to 54. The disclosure of which is hereby incorporated by reference.
Ordinarily, user information required by respective applications can be classified into information such as a name to be shared with or common to other applications and information such as a mail box specific to the pertinent application. Therefore, for a user, information shared with other applications and information specific to an application of the user are registered to respective directory entries and these entries are related to each other by a link.
As above, although the link is useful to express various information in a database, it has been desired to easily maintain the links in consideration of the system operation and management.
It is therefore an object of the present invention to provide a database link control method capable of easily establishing a link between records related to each other and a database system including a database link control function according to the method. Another object of the present invention is to provide, in the database system, a database server and/or a database client and a program to achieve the server and the client.
According to the present invention, there is provided a database system including a function to store information regarding a plurality of records and a link to relate records to each other. The database system holds at least one link generating information item to generate a link to relate records to each other.
Desirably, the database system of the present invention includes a database server including first storage means for storing information regarding at least one record and second storage means for storing a link to relate records to each other and a database client. The database client holds at least one link generating information item to generate a link between the records.
In the configuration, when the system operation manager beforehand defines a correspondence between respective records and stores the correspondence in the holding means, it is possible to register at least one link to the server at a time. Consequently, the system installation and operation can be carried out with considerably reduced human labor.
In a directory system including a data base to store information regarding at least one record and a function to store a link to relate records to each other, the database system of the present invention holds at least one link generating information item to generate a link to relate records to each other.
In this configuration, when the system operation manager beforehand defines a correspondence between respective entries and stores the correspondence in the holding means, at least one link can be registered to the server at a time. This remarkably minimizes human labor necessary for the system installation and operation.